The ever-increasing mobile traffic load leads to a pressing need for additional spectral resources of cellular systems, which are deployed in the spectrum mainly from 700 MHz to 2.6 GHz. More operators are now facing the challenge of soaring traffic with ever increasing number of people using mobile broadband services, as well as the traffic demand per person. While mobile broadband system in licensed spectrum is highly efficient due to its exclusive occupancy of the spectrum, the amount of available licensed spectrum can be limited and costly.
On the other hand, the amount of unlicensed spectrum assigned or currently planned to be assigned is comparable to or even more than the amount of licensed spectrum. To further expand mobile broadband system in licensed spectrum to meet the traffic demands, such as Long Term Evolution (LTE) system, a natural way is to integrate unlicensed carrier into the overall LTE system by adapting LTE protocols to operate in the unlicensed spectrum, named as LTE Unlicensed (LTE-U) or as License Assisted Access (LAA) using LTE. Extending the benefits of LTE to unlicensed spectrum brings its basic tenets of high-efficiency and robust mobility, while also making it a seamless extension of the larger LTE network. That means higher performance for operators and better broadband experience for users, and a common unified network for all spectrum types.